It is one of the marks of John McEnroe's brilliance as a tennis player that he has been half of several of the sport's great rivalries: McEnroe-Bjorn Borg, McEnroe-Jimmy Connors, McEnroe-Ivan Lendl.

Now, at the height of his skills, McEnroe might well become a part of another rivalry: McEnroe vs. the new generation of Swedes.

Today, in the 100-degree heat of Roland Garros, McEnroe and Joakim Nystrom produced another French Open classic, scrapping and scratching through five sets before McEnroe prevailed, 6-7 (1-7), 6-2, 6-2, 3-6, 7-5, to reach the semifinals.

"The match seemed to have everything you could want," McEnroe said. "After the third set, I thought I had the momentum but then he came back, mixed things up and took it away. It just went back and forth. By the end of the last set, we both had the shakes."

With the victory, McEnroe has two-thirds of the Swedish triple he needs to reach a second straight final. Sunday, he defeated Henrik Sundstrom. Today, it was Nystrom. Friday, he will play fourth-seeded Mats Wilander, a 6-4, 7-6 (7-5), 6-7 (5-7), 7-5 victor today over France's last hope, Henri Leconte.

Like the match before it, Leconte-Wilander was a roller coaster. Leconte served for the second set at 5-4, was broken and lost it in a tie breaker. Wilander was up a break in the third, lost it and dropped a tie breaker. Finally, Wilander served for the match in the fourth set, was broken and responded by saving a game point while leading at 6-5 before blasting two backhands to close out the match.

McEnroe is 5-3 against Wilander and 15-6 against the five Swedes in the world's top 15.

Before the sun had climbed high in the sky to wilt the men, Chris Evert Lloyd had reached the semifinals in a Grand Slam event for the 40th time in 41 career tries, cruising past 18-year-old Terry Phelps, 6-4, 6-0. Phelps admitted she was intimidated playing Evert because, "I grew up idolizing her."

Evert will play another teen-ager in the semifinals, Gabriela Sabatini. The 15-year-old Argentine became the youngest player to reach the French semifinals when she played a nearly flawless third set to upset fourth-seeded Manuela Maleeva, 6-3, 1-6, 6-1.

Today, though, was McEnroe's day. Although he has had moments of less than exemplary behavior here, McEnroe is well-liked by the French crowd. Today, when it became apparent he was in trouble, the fans rallied behind him.

"The crowd helped," McEnroe said. "When I got tired, they kind of gave me a rush. On a day like today, anything helps."

McEnroe needed every ounce of energy he had. Nystrom, 22, might be the quickest of the Swedes, and with the court fast and dry today he was able to run down innumerable balls because of the high red clay bounce.

After botching a 4-1 lead to lose the first set, McEnroe seemed in command when he won the next two sets at 6-2, taking eight straight games during one stretch.

And then . . . . "I let down at the start of the fourth set," McEnroe said.

Nystrom broke McEnroe in the second game of that set when McEnroe made three errors, the last a wide forehand. He served out the set from there, saving two break points in the fourth game and started the fifth set with a break, nailing a forehand return down the line at 15-40 for the break.

"When I got that break I thought I had a good chance to win," Nystrom said.

McEnroe was, by his admission, "very frustrated with myself" and was talking to himself and others. At one point, he looked behind him when he heard French Federation President Philippe Chatrier talking and said, "Are you finished now, Philippe, or are you going to chat with a few more people?"

But McEnroe hung in even after blowing two more break points in the second game of the set.

"It was tough not to get down. In fact I was down," McEnroe said. "But I had had chances and I had beaten the guy 6-2 in two sets. Down, 2-0, in the fifth I just kept thinking it could turn around at any time."

It finally turned around with Nystrom serving at 3-2. At 30-all, McEnroe followed a backhand in and punched a hard forehand volley for a winner. On break point, Nystrom tried for a drop backhand. McEnroe sprinted to the ball, leaned forward as far as he could and scooped a forehand cross court. Nystrom had guessed he would go down the line.

As the crowd roared, McEnroe punched the air and yelled, "Yeah!"

Nystrom shrugged at the memory: "I hit it too hard," he said.

McEnroe had forgotten the heat now and was flying. He held serve at love and broke Nystrom again, slamming a backhand off a looped topspin forehand for a seemingly safe 5-3 lead.

"At that point I really thought I would serve out the match," McEnroe said. "But he just hit one hell of a return on match point. He hit a desperation shot and it was perfect."

The match point came after McEnroe had saved a break point and followed with a big serve. On match point, he twisted in another high-kicking first serve and then watched in amazement as Nystrom sliced it down the line to stay alive.

"He was unlucky," Nystrom said graciously. "He hit a very good serve and I sliced a backhand just in. The slice could just have easily ended up in the fence."

But it didn't and McEnroe, shaken, netted a backhand and double-faulted to give the break back. Nystrom quickly held at love and it was 5-5. By now the court was a cauldron of noise and tension.

McEnroe walked to the back fence and untied and tied his sneakers trying to gather his thoughts. "I needed to take a breather and regroup," he said. "The game he served was over so fast it shocked me a little. I told myself it was just even again and I shouldn't throw the match away. I had the wind and I really wanted to hold serve right there."

He did, coming back from 15-30 down. That put the pressure back on Nystrom. He got to 40-30 with a backhand winner, but netted a lunging backhand volley for deuce. Finally, McEnroe followed a backhand return in and poked a backhand volley past Nystrom's dive for match point.

This time there was no luck for Nystrom. He ran down a hard forehand but pushed his backhand wide as McEnroe leaped for joy. As he walked off, McEnroe turned to all four sides of the stadium and waved his racket in salute.

"By the end, it was like one shot's difference either way," he said. "When you win a match like this, where you're up and down, up and down, it's a great feeling."